The Asymmetrical Electromagnetic Systems, disregarded -so far- by Science and EE, offer the advantages of exchanging components , (meaning using 'common' Coils for both) from Generator to Motor and viceversa...Like Tesla patented in this case, which is not the only one...
Physics states that a Motor is also a Generator, and a Generator is a Motor, however they can NOT perform "Both Duties" at the same time...of course not...IF We are referring to Symmetrical Electromagnetic Systems...but simply, that statement does NOT "Apply" to Asymmetrical Systems...

Below is an Image from same Patent 390414, where it is demonstrated the possible fusion between both machines...Motor (Exciter called by Tesla here) and Generator...